The most commonly used number system is decimal. This is based on the number 10 and numbers in the system use the digits 0 to 9. That is ten digits in all. An example of a 10 based number is 123. This can be thought of as: 1 one hundred, plus 2 tens, plus 3 ones. The table below shows how this can be represented.

hundreds	tens	ones
1	2	3

123 = 1x100 + 2x10 + 3x1

The hundreds, tens and ones are all powers of 10. They can be written in the following way. Note: It is a law of Mathematics that any number to the power of 0 is always 1.

102	101	100
1	2	3

123 = 1x10² + 2x10¹ + 3x10⁰

Here is another example.

1000 = 103	100 = 102	10 = 101	1 = 100
6	7	4	9

6742 = 6x10³ + 7x10² + 4x10¹ + 9x10⁰